Vehicles with leaning capability have improved performance and safety. One embodiment of a leaning vehicle, illustrated as a snowmobile 10, is illustrated in FIG. 1a. While a snowmobile is specifically illustrated, similar leaning suspensions are used on other types of vehicles, e.g., cars, trucks, off-road vehicles, all-terrain vehicles, etc. Snowmobile 10 leans into turns so that skis 30 and 32 carve through snow similar to a skier's skis. Leaning of snowmobile 10 is facilitated by a front suspension 34, shown separate from the snowmobile in FIG. 1b, which attaches skis 30 and 32 to snowmobile 10 and actuates the skis. Hydraulic shocks 68 and 88 are used by suspension 34 to actuate suspension arms 64 and 66. Suspension arms 64 and 66 each forms a parallelogram that is leaned over by force of hydraulic shocks 68 and 88 to lean snowmobile 10. FIG. 1c illustrates hydraulic shock 68 expanded, and hydraulic shock 88 collapsed, to lean suspension 34 toward the right of snowmobile 10. Snowmobile 10 is leaned toward the left by expanding shock 88 and collapsing shock 68.
FIG. 1d illustrates hydraulic system 120 that leans suspension 34 by actuating hydraulic shocks 68 and 88. Pump assembly 126 includes electric motors and a hydraulic pump that modify hydraulic pressure in the system to actuate hydraulic shocks 68 and 88. Hydraulic fluid is pumped out of shock 68 and into shock 88 to collapse shock 68 and expand shock 88. FIG. 1e illustrates details of pump assembly 126 from FIG. 1d in one embodiment. Electric motors 260 are controlled by a computer system. Electric motors 260 operate hydraulic pump 262 through pulleys 266 and 268, connected by belts 270. When pulley 268 is turned, hydraulic pump 262 pulls hydraulic fluid from one hose 128 and forces the hydraulic fluid out a second hose 128. Changing the direction that pulley 268 is turned changes which hose 128 is losing fluid and which is receiving additional fluid. In some embodiments, an electric motor and hydraulic pump are coupled without using belts, e.g., by direct coupling to a common shaft or by other suitable means.
As illustrated, hydraulic system 120 is a closed system. All hydraulic fluid transferred between shock 68 and shock 88 is forced through hydraulic pump 262. During some input events to suspension 34, one hydraulic shock 68 or 88 may be under significantly elevated hydraulic pressure. An input event to the suspension system can be a change in terrain, e.g., a rock or bump hit by the snowmobile, which applies a significant force to the system. The elevated pressure forces hydraulic fluid through the pump and shocks at an increased rate that heats the hydraulic fluid, reduces efficiency, and increases wear and tear on hydraulic pump 262.
Functioning of suspension 34 is more thoroughly explained in U.S. patent application Ser. No. 14/191,292 filed Feb. 26, 2014, now U.S. Pat. No. 9,545,976 issued Jan. 17, 2017, the disclosure of which is incorporated herein by reference.